Ionization vacuum gage with a switch-operated starting device and a microammeter begins functioning quickly in a high vacuum. The microammeter is also protected by its circuit design from spurious currents

Garwood, D. C.

English

NASA Technical Reports Server

er Cylinder 
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February 1965
	
Brief 65-10036 
NASA TECH BRIEF H 
NASA Tech Briefs are issued by the Technology Utilization Division to summarize specific 
technical innovations derived from the space program. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia, 22151. 
Ionization Vacuum Gage Starts Quickly, Is Unaffected by Spurious Currents 
The problem: Typical ionization vacuum gages 
require appreciable time to begin functioning in a very 
high vacuum because there is very little gas to ionize 
for production of measurement electrons. Addition-
ally, due to construction features and electrical 
paths, soft X-rays may be produced in conventional 
gages. These X-rays can cause electron emission from 
end plates and result in false indications of the vacuum 
being measured. 
The solution: An ionization vacuum gage that in-
cludes a switch-operated starting device and a 
measurement instrument (microammeter) that is pro-
tected by circuit design from any spurious currents. 
How it's done: A long outer cylinder surrounds a 
central anode that is a concentric inner cylinder. A
magnet around the outer cylinder provides a magnetic 
field within that cylinder in the direction of its axis. 
The inner cylinder is connected to a microammeter, to 
a dual negative source totaling four kilovolts, and then 
to ground. Connection of the inner cylinder to the 
negative potential allows the outer cylinder to be 
grounded instead of being connected to a positive 
potential and insulated. This greatly simplifies mount-
ing of the device. The length of the outer cylinder is 
equal to or longer than its diameter. This permits the 
electrons to remain within the chamber long enough to 
obtain sufficient ion current for convenient operation 
of the gage with only one end plate. Elimination of 
one end plate allows that end of the cylinder to be 
open to the vacuum to be measured. The end plate 
used is insulated from the outer cylinder and is 
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States Govern-
ment, nor NASA, nor any person acting on behalf of NASA: A. Makes 
any warranty or representation, express or implied, with respect to the 
accuracy, completeness, or usefulness of the information contained in
this document, or that the use of any information, apparatus, method, 
or process disclosed in this document may not infringe privately-owned 
rights; or B. Assumes any liabilities with respect to the use of, or for 
damages resulting from the use of, any information, apparatus, method, 
or process disclosed in this document.
https://ntrs.nasa.gov/search.jsp?R=19650000036 2020-03-11T17:17:07+00:00Z
connected to a point on the negative potential in 
between the potentials of the inner and outer cylinders. 
This accomplishes a dual purpose: current flowing 
from the end plate due to spurious emission of elec-
trons not related to gas ionization will not register 
on the microammeter; also, with the end plate at a 
higher potential than the inner cylinder, the latter 
receives over 90% of the ion current. 
When very high vacuums are to be measured, the 
switch is closed applying a positive potential to the 
inner cylinder which heats up and emits some elec-
trons to start the gage working quickly.
Note: 
Inquiries concerning this invention may be di-
rected to:
Technology Utilization Officer 
Jet Propulsion Laboratory 
4800 Oak Grove Drive 
Pasadena, California, 91103 
Reference: B65-10036 
Patent status: NASA encourages the immediate 
commercial use of this invention. Inquiries about 
obtaining rights for its commercial use may be made 
to NASA, Code AGP, Washington, D.C., 20546. 
Source: Donald C. Garwood 
(J PL-304) 
Brief 65-10036	 Category No. 02


Ionization vacuum gage starts quickly, is unaffected by spurious currents

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